The War to End All Wars. Though in 20 years time the Second World War would begin and the 78 million casualties would more than double the amount of World War One.

The total number of casualties in World War I, both military and civilian, was about 38 million: 16 million deaths and 22 million wounded (7 million were permanently disabled, and 15 million were seriously injured).

Of the 60 million European soldiers who were mobilized from 1914 – 1918, the official number of deaths was 9,721,937 with 21,228,813 wounded personnel; that is over half the military population. The Entente Powers (also known as the Allies -- United Kingdom, France, the Russian Empire, Belgium, Serbia, Canada, Australia, Italy, Japan, Greece, Romania and the United States) lost 5.7 million soldiers and the Central Powers (Germany, Austria-Hungary, Turkey, Bulgaria) about 4 million. Civilian deaths officially totaled 6,821,248, though many estimates double that number.

Germany lost 15.1% of its active male population, Austria–Hungary lost 17.1%, and France lost 10.5%. About 750,000 German civilians died from starvation brought on by the British blockade during the war. In 1914 alone, the typhus epidemic killed 200,000 in Serbia and a few years later more than 3 million more would die in Russia. By 1918, famine had killed approximately 100,000 people in Lebanon. In addition, the biggest influenza pandemic of the century, the Spanish flu, spread around the world killing at least 50 million to as many as 100 million people. Though the war was not the cause of the flu, it certainly hastened the pandemic (the first cases were found at the army base, Fort Riley, Kansas). With massive troop movements, close quarters and poor sanitary conditions, some researchers speculate that the soldiers' immune systems were weakened by malnourishment as well as the stress of combat and attacks from chemical weapons, increasing their vulnerability to the flu, widening the spread of the disease.